The trend in CMOS devices is toward decreased size. However, scaling down in size generally degrades device performance. In order to address issues in planar CMOS devices, vertical devices have been developed. Vertical architectures can increase device density and improve performance. For example, fin field effect transistors (finFETs) have been developed. FinFETs may have better electrostatic or short channel effect (SCE) control than planar CMOS devices. Density and effective emitter width (Weff) efficiency are independent of gate length (Lg), which allows more relaxed Lg for vertical devices. FinFET devices are thus replacing planar CMOS devices at smaller scales.
Performance of vertical devices is still desired to be improved. Mechanisms for improving performance other than varying Lg are limited because of tight density within a specific layout for such devices. Thus, research in vertical device architectures is ongoing.